Vehicle control device

ABSTRACT

A vehicle control device includes at least one electronic control unit configured to recognize at least one object, calculate a time to collision, operate first driving assistance, when the time to collision is equal to or less than a first threshold value, operate second driving assistance for avoiding the collision between the at least one object and the host vehicle or reducing damage of the collision, when the time to collision is equal to or less than a second threshold value smaller than the first threshold value, and set, while the first driving assistance is operated, the second threshold value to a second setting value smaller than a first setting value set when the first driving assistance is not operated, when a second target object causing the second driving assistance to operate is the same object as a first target object causing the first driving assistance to operate.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-188402 filed onSep. 28, 2017 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a vehicle control device including a functionof assisting driving of a vehicle by a driver.

2. Description of Related Art

In a related art, a precrash safety system (hereinafter, referred to asPCS) that recognizes an object in front of a vehicle using a sensor, andavoids a collision with the object or reduces damage due to a collisionis realized. Japanese Unexamined Patent Application Publication No.2017-114429 (JP 2017-114429 A) discloses that when a predeterminedcollision avoidance operation is performed by a driver, the driver isdetermined to have an intention of avoiding a collision and an operationtiming of the PCS is delayed such that the driver does not feel trouble.

SUMMARY

In order to further improve a collision avoidance performance, anotherapplication different from the PCS is studied to be mounted on a vehicletogether with the PCS. The application is a system that operates at atiming earlier than the PCS operation to cause a driver to recognizedanger of a collision. Hereinafter, the system is referred to as adanger avoidance system.

When the danger avoidance system is operated, there is a highpossibility that the driver recognizes the danger of the collision andperforms an operation to avoid the collision. At the time, the PCSoperation earlier than the collision avoidance operation of the drivermay cause trouble to the driver. As a countermeasure for the trouble,the delay of the operation timing of the PCS is considered when thedanger avoidance system is operated as when the driver performs thecollision avoidance operation in the related art.

However, an object different from the object that causes the dangeravoidance system to operate is assumed to approach a host vehicle. Forexample, another object may jump out from a side while the dangeravoidance system is operated on an object in front of a host vehicle. Insuch case, since the driver may not recognize the other object, a senseof security provided to the driver deteriorates when the operationtiming of the PCS is delayed.

The disclosure provides a vehicle control device capable of reducingtroublesome feeling of a driver by operating two types of drivingassistance having different operation timings without deteriorating asense of security provided to the driver.

An aspect of the disclosure provides a vehicle control device includingat least one electronic control unit configured to recognize at leastone object in front of a host vehicle using a sensor, calculate a timeto collision of the at least one object with respect to the hostvehicle, operate first driving assistance for avoiding danger of acollision between the at least one object and the host vehicle, when thetime to collision is equal to or less than a first threshold value,operate second driving assistance for avoiding the collision between theat least one object and the host vehicle or reducing damage of thecollision, when the time to collision is equal to or less than a secondthreshold value smaller than the first threshold value, and set, whilethe first driving assistance is operated, the second threshold value toa second setting value smaller than a first setting value, the firstsetting value being set when the first driving assistance is notoperated, when a second target object causing the second drivingassistance to operate is the same object as a first target objectcausing the first driving assistance to operate, the first target objectand the second target object being among the at least one object.

In the first driving assistance and the second driving assistance, thefirst driving assistance having a large threshold value with respect tothe time to collision is first operated in general. With the vehiclecontrol device configured as described above, the operation timing ofthe second driving assistance is delayed for the same object as theobject that causes the first driving assistance to operate, that is, anobject with a high possibility of recognition of the danger of thecollision by the driver. According to the above description, troublesomefeeling of the driver for the operation of the second driving assistancefollowing the operation of the first driving assistance is suppressed.On the other hand, the operation timing of the second driving assistanceremains as a normal timing for an object different from the object thatcauses the first driving assistance to operate, that is, an object thatthe driver may not recognize the danger of the collision. According tothe above description, a sense of security provided to the driver by theoperation of the second driving assistance improves.

In the vehicle control device according to the aspect of the disclosure,the at least one electronic control unit may be configured to cancel theoperation of the first driving assistance when a driver performs adanger avoidance operation during the operation of the first drivingassistance.

The performing of the danger avoidance operation by the driver isdetermined that the driver recognizes the danger of the collision.According to the above description, the troublesome feeling of thedriver due to a continuous operation of the first driving assistanceeven though the driver performs the danger avoidance operation issuppressed.

In the vehicle control device according to the aspect of the disclosure,the at least one electronic control unit may be configured to set thesecond threshold value to the first setting value, when the operation ofthe first driving assistance is canceled by the danger avoidanceoperation. That is, when the driver performs the danger avoidanceoperation to release the operation of the first piece of drivingassistance, the operation timing of the second piece of drivingassistance may be returned to a normal operation timing.

The operation of the first driving assistance may be canceled eventhough the danger avoidance operation by the driver is not sufficient.According to the above description, deterioration of the sense ofsecurity provided to the driver due to the delay of the operation timingof the second driving assistance is suppressed.

In the vehicle control device according to the aspect of the disclosure,the at least one electronic control unit may be configured to operatethe first driving assistance using an application different from anapplication operating the second driving assistance.

In the vehicle control device according to the aspect of the disclosure,the danger avoidance operation may include at least one of an operationof a brake or a steering wheel.

In the vehicle control device according to the aspect of the disclosure,the at least one electronic control unit may be configured to set, whilethe first driving assistance is operated, the second threshold value tothe first setting value, when the second target object is a differentobject from the first target object.

As described above, according to the aspects of the disclosure, thetroublesome feeling of the driver can be reduced by operating the twotypes of driving assistance having the different operation timingswithout deteriorating the sense of security provided to the driver.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a block diagram showing a configuration of a vehicle controldevice according to an embodiment of the disclosure;

FIG. 2 is a diagram for describing a setting of each target area of adanger avoidance system and a PCS;

FIG. 3 is a diagram for describing a process executed when an objectenters the target area of the danger avoidance system;

FIG. 4 is a diagram for describing a process executed when the objectthat enters the target area of the danger avoidance system furtherenters the target area of the PCS;

FIG. 5 is a diagram for describing a process executed when one objectenters the target area of the danger avoidance system in a case where aplurality of objects is recognized;

FIG. 6 is a diagram for describing a process executed when an objectdifferent from the object that enters the target area of the dangeravoidance system enters the target area of the PCS;

FIG. 7 is a flowchart showing a flow of driving assistance control foravoiding a collision according to Embodiment 1;

FIG. 8 is a diagram for describing a process executed when a driverperforms a danger avoidance operation after the object enters the targetarea of the danger avoidance system;

FIG. 9 is a diagram for describing a process executed when the driverperforms the danger avoidance operation after the object enters thetarget area of the danger avoidance system; and

FIG. 10 is a flowchart showing a flow of driving assistance control foravoiding a collision according to Embodiment 2.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described withreference to drawings. However, when a number such as the numbers ofrespective elements, quantity, amount, or range is mentioned in thefollowing embodiments, the disclosure is not limited to the mentionednumbers excluding a case where the numbers are particularly stated andare obviously specified in principle. Structures described in thefollowing embodiments are not necessarily required for the disclosureexcluding a case where the structures are particularly stated and areobviously specified in principle.

Embodiment 1

1-1. Configuration of Vehicle Control Device

A vehicle control device according to an embodiment of the disclosure isa device that assists driving of a vehicle by a driver so as to detect apossibility of a collision of a host vehicle on which the device ismounted and to avoid the collision. FIG. 1 is a block diagram showing aconfiguration of the vehicle control device according to the embodimentof the disclosure. A configuration of the vehicle control devicedescribed here is common not only to Embodiment 1 but also to Embodiment2 described below.

As shown in FIG. 1, a vehicle control device 10 is configured to take insignals from various sensors 2, 3, 4, and 5 attached to the vehicle, andto operate various actuators 6, 7 and a human machine interface (HMI) 8by operation signals obtained by processing the signals. The varioussensors 2, 3, 4, and 5 include vehicle sensors 2, 3 that acquireinformation relating to a motion state of the vehicle and autonomousrecognition sensors 4, 5 that acquire pieces of information relating toa surrounding environment and a peripheral object of the vehicle.Specifically, the vehicle sensors include a vehicle speed sensor 2 thatmeasures a traveling speed of the vehicle from rotation speeds oftire-wheel assemblies and a yaw rate sensor 3 that measures a turningangular speed of the vehicle. An acceleration sensor (not shown) is alsoone of the vehicle sensors. The autonomous recognition sensors include amillimeter wave sensor 4 provided, for example, in a front grille of thevehicle and a camera sensor 5 provided, for example, in a windshield ofthe vehicle. The camera sensor is configured as a stereo camera capableof measuring, for example, a distance to an imaging target. The sensors2, 3, 4, and 5 described above are connected to the vehicle controldevice 10 directly or through a communication network such as acontroller area network (CAN) constructed in the vehicle.

The various actuators 6, 7 include a braking actuator 6 for deceleratingthe vehicle and a steering actuator 7 for steering the vehicle. Thebraking actuator 6 is, for example, a hydraulic brake. However, when thevehicle is a hybrid vehicle or an electric vehicle, a power regenerativebrake is also included in the braking actuator 6. The steering actuator7 is a motor or a power steering system using hydraulic pressure. TheHMI 8 is an interface for outputting and inputting of informationbetween the driver and the vehicle control device 10. The HMI 8includes, for example, a display for displaying image information to thedriver, a speaker for outputting a sound, and a touch panel for thedriver to perform an input operation.

The vehicle control device 10 is an electronic control unit (ECU) havingat least one central processing unit (CPU), at least one read onlymemory (ROM), and at least one random access memory (RAM). Variouspieces of data including various programs and maps for avoiding thecollision are stored in the ROM. The vehicle control device 10 loads theprograms stored in the ROM on the RAM and causes the CPU to execute theprograms to realize various functions. The vehicle control device 10 maybe configured to have a plurality of ECUs. In FIG. 1, functionsparticularly related to the collision avoidance among the functionsincluded in the vehicle control device 10 are represented by blocks.Illustration of other functions included in the vehicle control device10 is omitted.

When an object is present in front of the host vehicle, the vehiclecontrol device 10 has a function of detecting the possibility ofcolliding with the object and of performing driving assistance foravoiding the collision. The functions described above are realized by ahost vehicle information acquisition unit 11, an object recognition unit12, a danger avoidance system calculation unit 20, a PCS calculationunit 30, an assistance arbitration unit 41, an automatic brakingcontroller 42, an automatic steering controller 43, and a notificationcontroller 44 included in the vehicle control device 10. However,configuration elements described above are not present as hardware inthe vehicle control device 10 and are realized by software when theprograms stored in the ROM are executed by the CPU.

The host vehicle information acquisition unit 11 acquires informationfrom the vehicle sensors such as the vehicle speed sensor 2 and the yawrate sensor 3 and calculates the motion state of the host vehicle basedon the acquired information. The host vehicle information acquisitionunit 11 predicts a path of the host vehicle from the motion state of thehost vehicle. An actual steering angle acquired by a steering anglesensor (not shown) may be used for predicting the path of the hostvehicle in addition to a vehicle speed and a yaw rate. The host vehicleinformation acquisition unit 11 updates a reference coordinate systemconstructed on a computer in accordance with the predicted path. Thereference coordinate system sets a direction of the predicted path ofthe host vehicle as the Y-axis and sets the width direction of the hostvehicle as the X-axis with a base point taken on the host vehicle as thecenter.

The object recognition unit 12 recognizes an object around the hostvehicle. Information acquired from the autonomous recognition sensorsuch as the millimeter wave sensor 4 and the camera sensor 5 is used forrecognizing the peripheral object. The object recognition unit 12 canrecognize the peripheral object by at least one method of, for example,using information of the millimeter wave sensor 4, using information ofthe camera sensor 5, or using the information of the millimeter wavesensor 4 and the information of the camera sensor 5 in combination bysensor fusion. The peripheral object to be recognized includes a movingobject such as a pedestrian, a two-wheeled vehicle, or an automobile,and a stationary object such as a stopped vehicle, a guardrail, abuilding, or a tree. The object recognition unit 12 processes a capturedimage obtained by the camera sensor 5 to recognize a section line suchas a roadway outside line or a roadway center line. The objectrecognition unit 12 calculates a position coordinate of a recognizedobject in the reference coordinate system.

The danger avoidance system calculation unit 20 determines whether tooperate a danger avoidance system. When determination is made thatdanger of the collision between the object in front of the host vehicleand the host vehicle occurs, the danger avoidance system operates thebraking actuator 6 and the steering actuator 7 to avoid the danger ofthe collision. Specifically, the danger avoidance system calculationunit 20 includes a collision determination unit 21, an operation timingsetting unit 22, and an operation determination unit 23. The dangeravoidance system calculation unit 20 is an example of “first drivingassistance unit”, and the operations of the braking actuator 6 and thesteering actuator 7 by the danger avoidance system calculation unit 20are examples of “first driving assistance”.

A calculation result of the host vehicle information acquisition unit 11and a recognition result of the object recognition unit 12 are input tothe collision determination unit 21. The collision determination unit 21determines a need to operate the danger avoidance system based on astate of the host vehicle and a relative relationship between eachobject recognized by the object recognition unit 12 and the hostvehicle. In details, the collision determination unit 21 calculates apredetermined variable for collision determination for the objectrecognized by the object recognition unit 12. The variable for collisiondetermination is a parameter for determining dangerousness of thecollision between the object and the host vehicle and includes, forexample, a lateral position of the object. The lateral position is aposition in the width direction of the object with respect to the hostvehicle, that is, is an X coordinate of the object in the referencecoordinate system. For example, when there is an object having a lateralposition that is within a predetermined threshold value range, thecollision determination unit 21 determines that there is a need tooperate the danger avoidance system and approves the object as anoperation target of the danger avoidance system.

The operation timing setting unit 22 sets a timing of operating thedanger avoidance system based on the calculation result of the hostvehicle information acquisition unit 11 and the recognition result ofthe object recognition unit 12. In the embodiment, the vehicle controldevice 10 operates the danger avoidance system when a time to collision(hereinafter, referred to as TTC) of the object approved as theoperation target with respect to the host vehicle is equal to or lessthan a predetermined threshold value. Therefore, in the operation timingsetting unit 22, the threshold value with respect to the TTC(hereinafter, referred to as TTC threshold value for danger avoidancesystem) is set as an operation timing of the danger avoidance system.When the X-axis of the reference coordinate system is set as a distance(lateral position) and the Y-axis thereof is set as a time (TTC), anarea defined by the threshold value range of the lateral position and aTTC threshold value for danger avoidance system of the TTC is a targetarea where the danger avoidance system operates. The target area of thedanger avoidance system will be described more specifically in “1-2.Setting of Each Target Area of Danger Avoidance System and PCS”described below.

The operation determination unit 23 determines whether to operate thedanger avoidance system. Specifically, the operation determination unit23 calculates a TTC of the object approved as the operation target ofthe danger avoidance system with respect to the host vehicle usingpieces of information acquired from the host vehicle informationacquisition unit 11 and the object recognition unit 12. In details, adistance of the object with respect to the host vehicle is divided by arelative speed to calculate the TTC. When the TTC and the TTC thresholdvalue for danger avoidance system set by the operation timing settingunit 22 are compared with each other and the TTC is equal to or lessthan the TTC threshold value for danger avoidance system, the operationdetermination unit 23 determines to operate the danger avoidance system.

When the danger avoidance system is operated, the danger avoidancesystem calculation unit 20 operates any one of avoidance steeringassistance and deceleration assistance according to a situation. Thedeceleration assistance assists an operation of the braking actuator 6by the driver, and the avoidance steering assistance assists anoperation of the steering actuator 7 by the driver. For example, when anavoidance margin width can be ensured within a traveling lane of thehost vehicle, the avoidance steering assistance is operated withpriority over the deceleration assistance. On the other hand, when theavoidance margin width cannot be ensured within the traveling lane ofthe host vehicle, the avoidance steering assistance is not operated andthe deceleration assistance is operated. When the decelerationassistance is operated, a deceleration request is output from the dangeravoidance system calculation unit 20 to the assistance arbitration unit41. When the avoidance steering assistance is operated, an avoidancesteering request is output from the danger avoidance system calculationunit 20 to the assistance arbitration unit 41.

The PCS calculation unit 30 determines whether to operate the PCS. ThePCS is a system of automatically operating the braking actuator 6 andthe steering actuator 7 to avoid the collision or to reduce the damagedue to the collision when a possibility of collision between the objectin front of the host vehicle and the host vehicle is determined to behigh. In details, the PCS calculation unit 30 includes a collisiondetermination unit 31, an operation timing setting unit 32, and anoperation determination unit 33. The PCS calculation unit 30 is anexample of “second driving assistance unit”, and the operations of thebraking actuator 6 and the steering actuator 7 by the PCS calculationunit 30 are examples of “second driving assistance”.

A calculation result of the host vehicle information acquisition unit 11and a recognition result of the object recognition unit 12 are input tothe collision determination unit 31. The collision determination unit 31determines a need to operate the PCS based on a state of the hostvehicle and a relative relationship between each object recognized bythe object recognition unit 12 and the host vehicle. In details, thecollision determination unit 31 calculates a predetermined variable forcollision determination, for example, a lateral position for the objectrecognized by the object recognition unit 12. For example, when there isan object having the lateral position that is within a predeterminedthreshold value range, the collision determination unit 31 determinesthat there is a need to operate the PCS and approves the object as anoperation target of the PCS. There is no particular limitation, but thethreshold value range of the lateral position for determining the needto operate the PCS is preferably the same as or narrower than thethreshold value range of the lateral position for determining the needto operate the danger avoidance system.

The operation timing setting unit 32 sets a timing of operating the PCSbased on the calculation result of the host vehicle informationacquisition unit 11 and the recognition result of the object recognitionunit 12 based on an operation situation of the danger avoidance system.In the embodiment, the vehicle control device 10 operates the PCS when aTTC of the object approved as the operation target with respect to thehost vehicle is equal to or less than a predetermined threshold value.Therefore, in the operation timing setting unit 32, the threshold valuewith respect to the TTC (hereinafter, referred to as TTC threshold valuefor PCS) is set as an operation timing of the PCS. When the X-axis ofthe reference coordinate system is set as a distance (lateral position)and the Y-axis thereof is set as a time (TTC), an area defined by thethreshold value range of the lateral position and a TTC threshold valuefor PCS is a target area where the PCS operates. The target area of thePCS will be described more specifically in “1-2. Setting of Each TargetArea of Danger Avoidance System and PCS” described below.

Since the PCS is operated when the collision cannot be avoided eventhough the danger avoidance system is operated, the TTC threshold valuefor PCS configured to determine the operation timing of the PCS is setto a value which is smaller than the TTC threshold value for dangeravoidance system configured to determine the operation timing of thedanger avoidance system. Specifically, the TTC threshold value fordanger avoidance system is set to five seconds, and the TTC thresholdvalue for PCS is set to three seconds. However, the TTC threshold valuefor PCS is not a fixed value and is a variable value having a settingvalue that is changed according to the operation situation of the dangeravoidance system. The setting of the TTC threshold value for PCS will bedescribed in details in “1-2. Setting of Each Target Area of DangerAvoidance System and PCS” described below. The TTC threshold value fordanger avoidance system is an example of “first threshold value”, andthe TTC threshold value for PCS is an example of “second thresholdvalue”.

The operation determination unit 33 determines whether to operate thePCS. Specifically, the operation determination unit 33 calculates a TTCof the object approved as the operation target of the PCS with respectto the host vehicle using pieces of information acquired from the hostvehicle information acquisition unit 11 and the object recognition unit12. When the TTC and the TTC threshold value for PCS set by theoperation timing setting unit 32 are compared with each other and theTTC is within the TTC threshold value for PCS, the operationdetermination unit 33 determines to operate the PCS.

When the PCS is operated, PCS calculation unit 30 operates an alarm, thedeceleration assistance, and intervention braking. The decelerationassistance assists the operation of the braking actuator 6 by thedriver, and the intervention braking automatically operates the brakingactuator 6 to forcibly apply braking force. The deceleration assistanceby the PCS is adjusted such that deceleration larger than thedeceleration assistance by the danger avoidance system acts on thevehicle. The PCS calculation unit 30 first operates the alarm, thenoperates the deceleration assistance, and finally operates theintervention braking. When the alarm is operated, an alarm request isoutput from the PCS calculation unit 30 to the assistance arbitrationunit 41. When the deceleration assistance or the intervention braking isoperated, the deceleration request is output from the PCS calculationunit 30 to the assistance arbitration unit 41. When the avoidance marginwidth can be ensured within a traveling lane of the host vehicle, theavoidance steering assistance may be operated together with thedeceleration assistance (or intervention braking). When the avoidancesteering assistance is operated, the avoidance steering request isoutput from the PCS calculation unit 30 to the assistance arbitrationunit 41.

The assistance arbitration unit 41 arbitrates the requests from thedanger avoidance system calculation unit 20, the requests from the PCScalculation unit 30, and requests from another control system, andprovides the arbitrated requests to the automatic braking controller 42,the automatic steering controller 43, and the notification controller44. For example, the deceleration request provided to the automaticbraking controller 42 may be simultaneously output from the dangeravoidance system calculation unit 20 and the PCS calculation unit 30.Furthermore, the deceleration request may be output also from anadaptive cruise control system. The avoidance steering request providedto the automatic steering controller 43 may be also simultaneouslyoutput from the danger avoidance system calculation unit 20 and the PCScalculation unit 30. Furthermore, the deceleration request may be outputalso from a lane trace control system. When the requests aresimultaneously provided from a plurality of systems described above, anarbitration process determines a request to be realized according to apriority. The same employs in the alarm requests provided to thenotification controller 44. When there is a plurality of alarm requests,an alarm to be prioritized is determined by the arbitration process. Inan example of the priority, when there are the deceleration request fromthe danger avoidance system calculation unit 20 and the decelerationrequest from the PCS calculation unit 30, the deceleration request fromthe PCS calculation unit 30 is prioritized. The same also employs in theavoidance steering request. The avoidance steering request from the PCScalculation unit 30 is prioritized.

The automatic braking controller 42 is a driver configured to controlthe braking actuator 6. The automatic steering controller 43 is a driverconfigured to control the steering actuator 7. The notificationcontroller 44 is a driver configured to control the HMI 8. The automaticbraking controller 42, the automatic steering controller 43, and thenotification controller 44 respectively operate the braking actuator 6,the steering actuator 7, and the HMI 8 according to the requestsarbitrated by the assistance arbitration unit 41.

1-2. Setting of Each Target Area of Danger Avoidance System and PCS

A setting of each target area of the danger avoidance system and the PCSwill be described with reference to FIG. 2. A host vehicle 1 and apedestrian 60 which is the moving object are drawn in FIG. 2. The rightand left roadway outside lines 53, 51 are drawn by solid lines, and aroadway center line 52 is drawn by dotted lines. Furthermore, a targetarea 70 of the danger avoidance system and a target area 80 of the PCSare respectively drawn. FIG. 2 shows a positional relationship betweenthe host vehicle 1 and the target areas 70, 80 in the referencecoordinate system. Here, an object recognized by the object recognitionunit 12 is assumed to be solely the pedestrian 60. The pedestrian 60 isschematically drawn in FIG. 2. However, in an actual recognition processby the object recognition unit 12, all objects including the pedestrian60 are represented in rectangular shapes in the reference coordinatesystem and are recognized as target objects having size and movementvector.

The target area 70 of the danger avoidance system is an area where thedanger avoidance system is operated when an object is positioned insidethe area 70. The target area 70 is set in front of the host vehicle 1compared with an X-axis 102 of the reference coordinate system with abase point 101 taken at the center of the front end of the host vehicle1 as the reference. However, “in front of” here means the future viewedfrom the present time. That is, a dimension of the Y-axis (not shown)when the TTC is handled in the reference coordinate system is time, andthe time on the X-axis 102 is zero. A front distance of the target area70 corresponds to a TTC threshold value for danger avoidance system 111.A width of the target area 70 in an X-axis direction corresponds to thethreshold value range of the lateral position for determining the needto operate the danger avoidance system.

The target area 80 of the PCS is an area where the PCS is operated whenan object is positioned inside the area 80. The target area 80 is set infront of the host vehicle 1 compared with an X-axis 102 of the referencecoordinate system with the base point 101 taken at the center of thefront end of the host vehicle 1 as the reference. A front distance ofthe target area 80 corresponds to a TTC threshold value for PCS 121.Therefore, the front distance of the target area 80 is shorter than thefront distance of the target area 70. A width of the target area 80 inthe X-axis direction corresponds to the threshold value range of thelateral position for determining the need to operate the PCS. There isno particular limitation, but the width of the target area 80 in theX-axis direction is preferably the same as or narrower than the width ofthe target area 70 in X-axis direction.

FIG. 3 is a diagram for describing a process executed when thepedestrian 60 enters the target area 70 of the danger avoidance system.In a case where the lateral position of the pedestrian 60 is within thethreshold value range, when the TTC is equal to or less than the TTCthreshold value for danger avoidance system 111, the pedestrian 60 is inthe target area 70. When the pedestrian 60 enters the target area 70,the vehicle control device 10 operates the danger avoidance system withthe pedestrian 60 as the target. Simultaneously, the vehicle controldevice 10 decreases the TTC threshold value for PCS from the value 121to a value 122 and reduces the target area of the PCS from the area 80to an area 81. A process of changing the TTC threshold value for PCS isperformed by the operation timing setting unit 32 of the PCS calculationunit 30.

FIG. 4 is a diagram for describing a process executed when thepedestrian 60 who enters the target area 70 of the danger avoidancesystem further enters the target area (target area after reduction) 81of the PCS. In a case where the lateral position of the pedestrian 60 iswithin the threshold value range, when the TTC is equal to or less thanthe TTC threshold value for PCS 122, the pedestrian 60 is in the targetarea 81. When the pedestrian 60 enters the target area 81, the vehiclecontrol device 10 operates the PCS with the pedestrian 60 as the target.

The processes described in FIGS. 3 and 4 are processes when the objectthat causes the danger avoidance system to operate and the target thatcauses the PCS to operate are the same object (the same pedestrian 60).In the case, the TTC threshold value for PCS is set to a value which issmaller than a value when the danger avoidance system is not operated,and the target area that causes the PCS to operate is reduced. Accordingto the above description, since the operation timing of the PCS isdelayed for an object with a high possibility of recognition of thedanger of the collision by the driver, troublesome feeling of the driverfor the operation of the PCS following the operation of the dangeravoidance system is suppressed.

On the other hand, when there is a plurality of objects recognized bythe object recognition unit 12, a process different from the aboveprocesses may be performed. FIG. 5 is a diagram for describing a processexecuted when one object enters the target area 70 of the dangeravoidance system in the case where a plurality of objects is recognized.Two pedestrians 60A, 60B recognized by the object recognition unit 12are drawn in FIG. 5. Here, solely the pedestrian 60A is assumed to enterthe target area 70 of the danger avoidance system. In the case, thevehicle control device 10 decreases the TTC threshold value for PCS fromthe value 121 to the value 122 and reduces the target area of the PCSfrom the area 80 to the area 81 simultaneously operating the dangeravoidance system with the pedestrian 60A as the target.

However, the TTC threshold value for PCS is decreased solely for thepedestrian 60A. The operation timing setting unit 32 of the PCScalculation unit 30 sets the TTC threshold value for PCS for each objectrecognized by the object recognition unit 12. The operation timingsetting unit 32 maintains the TTC threshold value for PCS at a normalsetting value 121 and maintains the target area of the PCS at a normalsetting area 80 for the pedestrian 60B who does not enter the targetarea 70 of the danger avoidance system. That is, the operation timing ofthe PCS is delayed solely for the object (pedestrian 60A) that causesthe danger avoidance system to operate and remains as the normal timingfor the object (pedestrian 60B) different from the object (pedestrian60A) that causes the danger avoidance system to operate.

FIG. 6 is a diagram for describing a process executed when thepedestrian 60B different from the pedestrian 60A who enters the targetarea 70 of the danger avoidance system enters the target area 80 of thePCS. When a lateral position of the pedestrian 60B is within thethreshold value range and a TTC of the pedestrian 60B is equal to orless than the TTC threshold value for PCS 121, the pedestrian 60B is inthe target area 80. When the pedestrian 60B enters the target area 80,the vehicle control device 10 operates the PCS with the pedestrian 60Bas the target.

If the target area of the PCS for the pedestrian 60B is reduced from thearea 80 to the area 81, the PCS does not operate since the pedestrian60B is not in the area 81 in the example shown in FIG. 6. For thepedestrian 60A who is the operation target of the danger avoidancesystem, there is a high possibility that the driver recognizes thepresence of the pedestrian 60A, but the driver may not recognize thepedestrian 60B who jumps out from a side. Consequently, when theoperation timing of the PCS is delayed, a sense of security provided tothe driver deteriorates. In the point, in the embodiment, since theoperation timing of the PCS remains as the normal timing for the object(pedestrian 60B) that the driver may not recognize the danger of thecollision, the sense of security provided to the driver by the operationof the PCS improves.

1-3. Driving Assistance Control for Avoiding Collision

The vehicle control device 10 configured as described above executesdriving assistance control for avoiding the collision while the driverdrives the host vehicle 1. FIG. 7 is a flowchart showing a flow of thedriving assistance control for avoiding the collision according toEmbodiment 1. The vehicle control device 10 repeatedly executesprocesses shown in the flowchart in a predetermined period.

A process in step S1 corresponds to the function of the host vehicleinformation acquisition unit 11. In step S1, the motion state of thehost vehicle is calculated based on the information from the vehiclesensors such as the vehicle speed sensor 2 and the yaw rate sensor 3,and the path of the host vehicle is predicted from the motion state ofthe host vehicle.

A process in step S2 corresponds to the function of the objectrecognition unit 12. In step S2, pieces of surrounding environmentinformation are recognized using the information acquired from theautonomous recognition sensor such as the millimeter wave sensor 4 andthe camera sensor 5, and further a target object is recognized from thepieces of surrounding environment information. In the process in stepS2, a type of a target object (automobile, pedestrian, two-wheeledvehicle, stationary object, or the like) and a position coordinate ofthe target object in the reference coordinate system are recognized.

Processes from steps S3 to S7 correspond to the function of the dangeravoidance system calculation unit 20. In step S3, a TTC threshold valuefor danger avoidance system (TTCr) is set. The TTC threshold value fordanger avoidance system is basically a fixed value, but the value may bechanged according to a state of the host vehicle.

In step S4, a TTC of an object that is the operation target of thedanger avoidance system is calculated. When there is a plurality ofobjects that are the operation targets of the danger avoidance system,the TTC is calculated for each object. In step S5, determination onwhether the TTC calculated in step S4 is equal to or less than the TTCris made. When there is a plurality of objects that are the operationtargets of the danger avoidance system, the determination in step S5 isalso made for each object.

When the TTC (at least one TTC when TTC is calculated for each of theobjects) calculated in step S4 is equal to or less than the TTCr, aprocess in step S6 is selected. In step S6, a flag (hereinafter,referred to as danger avoidance system operation flag) for operating thedanger avoidance system is turned on. When the process in step S6 isalso selected at the previous timing, the danger avoidance systemoperation flag is maintained to be on.

On the other hand, when the TTC (all TTCs when TTC is calculated foreach of the objects) calculated in step S4 is larger than the TTCr, aprocess in step S7 is selected. In step S7, the danger avoidance systemoperation flag is turned off. When the process in step S7 is alsoselected at the previous timing, the danger avoidance system operationflag is maintained to be off.

Processes from step S8 to step S16 correspond to the function of the PCScalculation unit 30. In step S8, an initial value of a TTC thresholdvalue for PCS (TTCp) is set. The initial value of the TTC thresholdvalue for PCS is basically a fixed value, but the value may be changedaccording to a state of the host vehicle.

In step S9, determination on whether the danger avoidance systemoperation flag is on is made. When the danger avoidance system operationflag is not on, a process in step S12 is selected. In step S12, theoperation timing of the PCS is maintained at the initial value bymaintaining the TTC threshold value for PCS at the initial value set instep S8.

When the danger avoidance system operation flag is on, in step S10,determination on whether the object that causes the danger avoidancesystem to operate and an object that is the operation target of the PCSare the same is made. That is, determination on whether the object thatsatisfies the condition in step S5 and the object that is the operationtarget of the PCS are the same is made.

When the object that causes the danger avoidance system to operate andthe object that is the operation target of the PCS are the same, aprocess in step S11 is selected. In step S11, a TTC threshold value forPCS for the object that is the operation target is smaller than theinitial value set in step S8. According to the above description, theoperation timing of the PCS for the object that is the operation targetis delayed compared with the initial value.

On the other hand, when the object that causes the danger avoidancesystem to operate and the object that is the operation target of the PCSare different from each other, a process in step S12 is selected. Instep S12, a TTC threshold value for PCS for the object that is theoperation target is maintained at the initial value set in step S8.According to the above description, the operation timing of the PCS forthe object that is the operation target is maintained at the initialvalue.

In step S13, a TTC of the object that is the operation target of the PCSis calculated. When there is a plurality of objects that are theoperation targets of the PCS, the TTC is calculated for each object. Instep S14, determination on whether the TTC calculated in step S13 isequal to or less than a TTCp is made. The TTCp used for thedetermination is the initial value set in step S8 when the process instep S12 is selected, and is a reduced value compared with the initialvalue when the process in step S11 is selected. When there is aplurality of objects that are the operation targets of the PCS, thedetermination in step S14 is also made for each object.

When the TTC (at least one TTC when TTC is calculated for each of theobjects) calculated in step S13 is equal to or less than the TTCp, aprocess in step S15 is selected. In step S15, a flag (hereinafter,referred to as PCS operation flag) for operating the PCS is turned on.When the process in step S15 is also selected at the previous timing,the PCS operation flag is maintained to be on.

On the other hand, when the TTC (all TTCs when TTC is calculated foreach of the objects) calculated in step S13 is larger than the TTCp, aprocess in step S16 is selected. In step S16, the PCS operation flag isturned off. When the process in step S16 is also selected at theprevious timing, the PCS operation flag is maintained to be off.

A process in step S17 corresponds to the functions of the assistancearbitration unit 41, the automatic braking controller 42, the automaticsteering controller 43, and the notification controller 44. In step S17,the braking actuator 6, the steering actuator 7, and the HMI 8 arecontrolled based on the danger avoidance system operation flag set instep S6 or S7 and the PCS operation flag set in step S11 or S12.Specifically, when the danger avoidance system operation flag is on, thebraking actuator 6 and the like are controlled so as to operate thedanger avoidance system or to maintain the operation of the dangeravoidance system. When the PCS operation flag is on, the brakingactuator 6 and the like are controlled so as to operate the PCS or tomaintain the operation of the PCS. However, when both the dangeravoidance system operation flag and the PCS operation flag are on, thePCS operation flag is prioritized.

Embodiment 2

2-1. Characteristics of Embodiment 2

Embodiment 2 is characterized by processes when the driver performs adanger avoidance operation during the operation of the danger avoidancesystem. Hereinafter, the characteristics will be described withreference to FIGS. 8 and 9. FIGS. 8 and 9 are diagrams for describingthe processes when the driver performs the danger avoidance operationafter the pedestrian 60 enters the target area 70 of the dangeravoidance system.

When the pedestrian 60 enters the target area 70 of the danger avoidancesystem, the danger avoidance system calculation unit 20 operates thedanger avoidance system. When the danger avoidance system operation flagis turned on, PCS calculation unit 30 decreases the TTC threshold valuefor PCS from the initial value to the value 122 and reduces the targetarea of the PCS from the normal setting area to the area 81. When thedriver performs the danger avoidance operation in the reduced state, thedanger avoidance system calculation unit 20 cancels the operation of thedanger avoidance system as shown in FIG. 8. The reason is that theperforming of the danger avoidance operation by the driver is determinedthat the driver recognizes the danger of the collision. The releasing ofthe operation of the danger avoidance system suppresses troublesomefeeling of the driver due to a continuous operation of the dangeravoidance system even though the driver operates the danger avoidanceoperation.

When the cancel of the operation of the danger avoidance system isreceived, the PCS calculation unit 30 resets the TTC threshold value forPCS from the value 122 to the initial value 121 and returns the targetarea of the PCS from the area 81 to the normal setting area 80 as shownin FIG. 9. That is, the operation timing of the PCS is returned to anormal operation timing. The reason is that the operation of the dangeravoidance system may be canceled even though the danger avoidanceoperation by the driver is not sufficient. The returning of theoperation timing of the PCS to the normal operation timing suppressesdeterioration of the sense of security provided to the driver due to thedelay of the operation timing of the PCS.

2-2. Driving Assistance Control for Avoiding Collision

FIG. 10 is a flowchart showing a flow of driving assistance control foravoiding a collision according to Embodiment 2. The vehicle controldevice 10 repeatedly executes processes shown in the flowchart of FIG.10 in a predetermined period. A common step number is assigned to aprocess having contents common to the driving assistance controlaccording to Embodiment 1 in the flowchart, and a description thereofwill be omitted.

In Embodiment 2, when the condition in step S5 is satisfied,determination on whether the driver performs the danger avoidanceoperation is made in step S21. The danger avoidance operation includes adeceleration operation of a brake and avoidance steering of a steeringwheel. When the driver does not perform the danger avoidance operation,the process in step S6 is selected and the danger avoidance systemoperation flag is turned on or maintained to be on. On the other hand,when the driver performs the danger avoidance operation, the process instep S7 is selected and the danger avoidance system operation flag isturned off.

In Embodiment 2, when the condition in step S9 is not satisfied, thatis, when the danger avoidance system operation flag is off,determination in step S22 is made. In step S22, the determination onwhether the danger avoidance system operation flag is on in the previoustime is made, that is, the determination on whether the danger avoidancesystem operation flag is switched from on to off from the previous timeto the present time is made. When the danger avoidance system operationflag is also off in the previous time, the process in step S12 isselected and the operation timing of the PCS is maintained at theinitial value that is the normal setting. On the other hand, when thedanger avoidance system operation flag is on in the previous time, aprocess in step S23 is selected and the operation timing of the PCS isreturned to the normal setting by resetting the TTC threshold value fordanger avoidance system (TTCp) to the initial value. When the process instep S12 or step S23 is selected, determination is made using the TTCpset to the initial value in step S14.

Another Embodiment

In Embodiments 1 and 2, when the TTC is equal to or less than the TTCthreshold value for danger avoidance system (TTCp), the alarm, thedeceleration assistance, and the intervention braking are operated inthe order. However, a TTC threshold value may be provided for each ofthe alarm, the deceleration assistance, and the intervention braking,and the operation determination may be made individually. Specifically,the alarm may be operated when the TTC is equal to or less than a TTCthreshold value for alarm (TTCp−alm), the deceleration assistance may beoperated when the TTC is equal to or less than a TTC threshold value(TTCp−pba) for deceleration assistance, and the intervention braking maybe operated when the TTC is equal to or less than a TTC threshold value(TTCp-pb) for intervention braking. However, there is a relationshipthat

TTCr≥TTCp−alm≥TTCp−pba≥TTCp−pb

between respective threshold values.

What is claimed is:
 1. A vehicle control device comprising at least oneelectronic control unit configured to recognize at least one object infront of a host vehicle using a sensor, calculate a time to collision ofthe at least one object with respect to the host vehicle, operate firstdriving assistance for avoiding danger of a collision between the atleast one object and the host vehicle, when the time to collision isequal to or less than a first threshold value, operate second drivingassistance for avoiding the collision between the at least one objectand the host vehicle or reducing damage of the collision, when the timeto collision is equal to or less than a second threshold value smallerthan the first threshold value, and set, while the first drivingassistance is operated, the second threshold value to a second settingvalue smaller than a first setting value, the first setting value beingset when the first driving assistance is not operated, when a secondtarget object causing the second driving assistance to operate is thesame object as a first target object causing the first drivingassistance to operate, the first target object and the second targetobject being among the at least one object.
 2. The vehicle controldevice according to claim 1, wherein the at least one electronic controlunit is configured to cancel the operation of the first drivingassistance when a driver performs a danger avoidance operation duringthe operation of the first driving assistance, and set the secondthreshold value to the first setting value, when the operation of thefirst driving assistance is canceled by the danger avoidance operation.3. The vehicle control device according to claim 1, wherein the at leastone electronic control unit is configured to operate the first drivingassistance using an application different from an application operatingthe second driving assistance.
 4. The vehicle control device accordingto claim 2, wherein the danger avoidance operation includes at least oneof an operation of a brake or a steering wheel.
 5. The vehicle controldevice according to claim 1, wherein the at least one electronic controlunit is configured to set, while the first driving assistance isoperated, the second threshold value to the first setting value, whenthe second target object is a different object from the first targetobject.